Country stalwart Blake Shelton and indie-rock/pop goddess Gwen Stefani seemed like an unlikely match from the start of their relationship -- so much so, that some actually wondered if their matchup was a publicity stunt. However, the duo is still going strong nearly two years in, and their fellow Voice coach, Adam Levine, is quick to assure fans that the couple is indeed the real deal.

“They’re so in love it’s disgusting,” Levine related on the Howard Stern Show Tuesday (Oct. 31). “I’m so affectionate and gross with my wife, [but] this is a whole other level of vomit. They’re so in love. It’s really nice.”

Levine added that he of all people should know what’s up: “Because [their relationship] is in the public eye, a lot of people want to have their own bulls--t opinions about it, but I’m, like, there,” he says. “I see it every day. I have a pretty unique perspective on it, and it’s real, man."

The Maroon 5 singer says he claims Shelton and Stefani as two of his closest friends -- but jokes, "I still tell [Blake], 'I can't believe you get to be with Gwen Stefani'…It's just not f---ing right!"

And as for what’s on every fan’s mind? No, Levine does not have any inside scoop on future wedding bells. He honestly has no idea if or when Shelton and Stefani will tie the knot, he told Stern, but noted that he hopes if they do, he will receive an invitation.

Shelton, 41, and Stefani, 48, met as coaches on The Voice working alongside Levine. They started dating not long after both went through very public and difficult divorces— Shelton’s from Miranda Lambert and Stefani’s from Gavin Rossdale.